1. Technical Field
The present invention relates to a droplet ejection apparatus, capable of ejecting droplets of plural types of different droplet volumes, and to a droplet ejection control apparatus and a method for droplet ejection of the same.
2. Related Art
Currently, ink jet printers are widely used that have a recording head arrayed with plural ejection apertures, and droplets of liquid ink are ejected by driving actuators that correspond with each ejection aperture with a predetermined voltage application cycle period, and printing on a printing medium. Among these, printers are known in which piezoelectric elements are used as actuators, and by application of driving signals of different driving waveforms to the piezoelectric elements, ink droplets of different droplet volume may be ejected according to the image data.
However, when the droplet volume of the ink droplets is changed the droplet speed (the speed required for the ejected droplets to adhere to the recording medium) also often changes. This difference in droplet speed due to the droplet volume gives rise to misalignment in the impact positions on the recording medium between the different droplet types, and this is a cause of deteriorating image quality (here, impact has the meaning of the adherence of ink or the like ejected from the recording head to paper or such like medium onto which the droplets are ejected).
Conventionally, analog driving waveforms are widely used wherein the shape of the waveform of the driving signal applied to a piezoelectric element may be arbitrary set in the time direction and the electrical voltage direction. In an analogue driving waveform, it is relatively easy to change the droplet volume without substantially changing the droplet speed. However, disadvantages are that the driving circuit for an analogue waveform is large, and the energy consumption is also large. Because of this the use of digital driving waveforms, generated by switching on and off digital switching elements connected to electrical voltages of two or three values, has become widespread. In this way driving circuits may be made compact and low cost, and reductions may be made in the energy consumption.